Two novel D-D-pi-A organic dyes (SDI and SD2) based on triphenylamine and indole donors are designed and synthesized for dye-sensitized solar cells (DSSCs). For the first time, an SCN group is introduced into a metal-free organic dye SD2. The effects of the SCN group on the photophysical, electrochemical and photovoltaic properties are investigated. It is found that the introduction of SCN group to the SD2 molecule leads to a higher molar extinction coefficient and better photovoltaic performances compared with dye SDI. Under AM 1.5G irradiation (100 mW cm(-2)), a maximum power conversion efficiency (n) of 6.74% is obtained for the SD2-based DSSCs, higher than that of SCN-free dyes SDI (eta = 5.53%). These results have demonstrated that the corporation of SCN group into the organic dye will be an effective approach to develop high-performance metal-free organic dyes. (C) 2013 Elsevier B.V. All rights reserved.